Condenser



Aug. 2l, 1951 D. D. JONES CONDENSER Original Filed Jan. 18, 1946 F'IG. 2

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Patented Aug. `2l, 1951 CONDENSER David D. Jones, Westport, Conn.,assignor to Western Electric Company, Incorporated, New York, N. Y., acorporation of New York Original application January 18, 1946, SerialN0.

642,044. Divided and this application November 6, 1948, Serial No.58,779

3 Claims. (Cl. F75-41.5)

This invention relates to condensers, and more particularly relates tocondensers for measuring pressures of material being extruded.

This application is a division of copending application, Serial No.642,044, filed January 18, 1946, by D. D. Jones for Pressure MeasuringApparatus, which is now Patent No. 2,457,902.

In the manufacture of insulated conductors, a conductor, which may bebare or covered, is sometimes advanced continuously through an extrusionhead of an extrusion apparatus of a type which includes an extrusionpassage in which an extrusion die is mounted and in which a core tubeand a core tube holder are positioned for centering the conductor withrespect to the extrusion die. The extrusion apparatus forces insulatingmaterial through the extrusion die under high pressures, whereby the dieforms the insulating material into a covering on the conductor. Theinsulating material is brought to the extrusion apparatus in batches andthe extrudability of the batches of insulating mate- When it varies, itnecessitates readjustment of the extrusion apparatus when a new batch ofinsulating material is extruded therethrough.

In the past, there has been no satisfactory means for determining theextrudability of each batch of insulating material without longexperimentation, and the extrusion apparatus had to be adjusted by trialand error methods to obtain the most advantageous adjustment thereof.One of the main reasons why the extrudability of the various batches ofinsulating material could not be ascertained, was that no means wereknown for measuring the pressure of the insulating material as theinsulating material was extruded. The high extrusion pressures of theinsulating material in the extrusion apparatus aggravated the problem,since they made imperative pressure testing means which wouldsatisfactorily withstand these high pressures.

An object of the invention is to provide new and effective condensers.

A further object of the invention is to provide new and eil'ectivecondensers for measuring pressures of insulated material being extrudedwithout interfering with the extrusion process.

A condenser illustrating certain features of the invention may include apair of conductive plates, a resilient dielectric plate for separatingthe conductive plates, and means for transmitting pressure to theconductive plates to compress the dielectric plate between them so as toincrease the capacity of the condenser.

A complete understanding of the invention may i circuit included in theapparatus.

Referring now in detail to the drawing, there is shown in Fig. 1 acontinuous extrusion apparatus provided with a condenser forming oneembodiment of the invention. The continuous extrusion apparatus isdesigned to apply a covering of plastic material, such as a vulcanizablerubber compound, upon a nlamentary conductor, which may be bare orcovered with a. textile or plastic covering. This apparatus includes abody portion I0 having a cylindrical extrusion bore Il formed therein inwhich a stock screw I2 is mounted. The stock screw is rotated bysuitable driving means, such as an electric motor and a gear train, (notshown) to force insulating material i3 through an extruding head i4under high pressure. The extruding head ,includes a body member i5having a tapered opening I6, which forms a continuation of the extrusionbore il and communicates with an extrusion passage 20 formed in theextruding head transversely of the tapered opening Il.

An annular die holder 2| is positioned in the exit end of the extrusionpassage 20 and has a counterbore 22 formed therein in which is mounted aforming` die 23. A conductor 24 is advanced toward the left, as viewedin Fig. 1, by suitable core-advancing means, such as a capstan (notshown) through a core tube holder 25 and a core tube 30, which is heldby the core tube holder 2l. The core tube holder 2l is provided with aninclined concave surface 26 for detlecting the insulating material i3toward the die 2l. An

aligning plate 3| maintains the die holder 2i,-

and the core tube holder 25, and thereby the core tube 30, centeredrelative to each other in the extrusion passage 20, and a retaining nut32 holds these elements in the extruding head Il.

The pressure of the insulating material Il in the extruding passage 20against the core tube J0 and the core tube holder 2l urges the core tubeholder against the left end of a plug al- 3 sembly u, which includes abolt I4 threaded into a bore Il formed in the extruding head i4. Acompressible, variable condenser il forms the left end of the plugassembly 8l, as seen in the drawing, and includa an annular collar 4l,which is provided with a cylindrical bore 4i therein. The annular collar4l has a nange 42 on the left end thereof and is secured to the bolt I4by bolts 43-4I. A bushing 44 composed of electrically insulatingmaterial is positioned within the condenser I! and within a metal thrustwasher 4l, which fits within the cylindrical bore 4l in the annularcollar and abuts the end of the bolt $4.

An annular backing plate Il, which is mounted in the cylindrical bore 4|of the annular collar 4l by bolts lI-Il and nuts "-42, abuts the thrustwasher 4l. Annular conductive plates Il, I4, Il and Il and resilient,annular dielectric plates GII, tl, l2, Il and t4 interleaving theconductive plates are mounted slidably on the bushing 44, between thebacking plate Il and a thrust washer 1l which is slidably mounted on theleft end of the bushing 44, as viewed in Fig. 2. The dielectric platesmay be composed of a hard rubber compound which is compressed to only aslight extent under high pressure and has the quality of retaining nopermanent deformation.

Normally a backing plate 1l rigidly secured to a central plug 12 havinga passage 1I therein is held against the thrust washer with apredetermined amount of force. This force is determined by a nut 14 anda lock nut 1l, which are threaded on the right hand end of the centralplug 12.

When theI core tube holder 2l is urged to the right, as viewed in Fig.1, by the insulating material I3, the force exerted thereon plus thatexerted on the core tube Il is transmitted to the dielectric plates 00,Il, l2, Il and I4 through the backing plate 1i and the thrust washer 10.This causes the dielectric plates to be compressed more than normallyand thereby decreases the distance between the conductive plates Il, 54,55 and It.

The annular collar has a passage 18 formed therein through which coolingwater 11, or other suitable coolant, flows to maintain the condenser 39under an even temperature so that-the heat of the body portion Ill,which is heated by steam in a steam passage 18 and the extruding headI4, which is heated by steam in a steam passage 19, does not affect thecondenser I! excessively.

An insulated conductor B0 connected to the conductive plates 5l and Ilpasses through a bore 8| formed in the backing plate 50, a bore 82formed in the thrust washer 4l and a bore 83 formed in the bolt 34. Aninsulated conductor 84 connected to the conductive plates 54 and 56extends through a bore Il formed in the backing plate 50, a bore I6formed in the thrust washer 4l and a bore l1 formed in the bolt 34. Theconductor lll is connected to an adjustable resistance lll (Fig. 3),connected by a conductor 9| to one output terminal of an electricaloscillator 92, which is of known design and has an output frequency ofaround 15,000 cycles per second. The oscillator 92 is energized by analternating current power line Il and the other output terminal thereofis connected by a conductor 84 to a suitable ammeter 9|. The conductorI4 also is connected to the ammeter 0l.

The force with which the insulating material Il presses the core tube iland the core tube holder 2l against the backing Plak 1l is equal to theunit pressure of the material multipliedbythetotalcfthetransverseareasoftbecoretubeandthecoretubeholderincontactwiththe insulating material which areknown. Since the totalcontacted transverseareasofdiecoretube and thecore tube holder are constant. the transmitted force is directlyproportional to the pressureoftheinsulatingmaterialonthecoretnbe and thecore tube holder. This force h exerted in compression upon thedielectric plates il. il and Il and decreases them inthicknem in directproportion to the amount of the force.

The capacity of each of three condensers including that formed by theconductive plate Il. the dielectric plate Il and the conductive plateI4, that formed by the conductive plate I4. the dielectric plate l! andthe conductive plate Il. and that formed by the conductive plate Il. thedielectric plate il and the conductive plate Il, may be expressedfundamentally by the formula KA Cza where C is the capacity, A is thearea of one of a pair of the conductive plates, K is the dielectricconstant of the dielectric plates, and d is the distance between thepair of conductive plates.

K and A are constants in each of the individual condensers Justdescribed so that C and d are the only variables and C is inverselyproportional to d. Hence, as d, the distance between each adjacent pairof the conductive plates, is decreased. C, the capacity of theindividual condenser. is proportionately increased. Since d decreasesdirectly with increases in the force compressing the dielectric plates.it follows that C is directly proportional to the pressure of theinsulating material Il. The three individual condensers of thecompressible condenser u are identical and are connected in parallel sothat the capacity of the condenser II is equal to the sum of thecapacities of the individual condensers thereof. Hence, the total changein capacity of the condenser 39 is three times the change of thecapacity of one of the three individual condensers thereof for any givenchange in the pressure of the insulating material Il.

The circuit including the oscillator l2 (Fig. 3), the adjustableresistance Il, the compressible condenser It, and the ammeter II isgoverned by the following formula:

Z=K+XC where K is a constant equal to the resistance 0f the resistance9| and Xc is the capacity reactance of the condenser il.

Substituting K+Xc for Z,

BincethevaluesofEandKai-econstant,

l INE Also.

l XC-2Tj;

where f is the frequency of the circuit and c is the capacity of thecondenser. Hence,

l, the frequency of the oscillator l! is constant so that it may be saidthat I is proportional only to c. which is the capacity of the condenseril, and varies in direct proportion to the pressure of the insulatingmaterial I3 in the extrusion passage 2l in the extruding head il.

'Ihe reading of the ammeter l5 is directly proportional to I and henceis directly proportional to the pressure on the insulating material i3in the extrusion passage in the extruding head Il. The ammeter iscalibrated in umts oi pressure and indicates the unit pressure on theinsulating material.

In the use of the pressure measuring apparatus forming a speciiicembodiment oi' the invention. the insulating material Il is extruded bythe extrusion apparatus under pressure and the pressure thereoncompresses the condenser Il thereby 4increasing its capacityproportionally. The reading o! the ammeter l! in the above-describedcircuit is proportional to the capacity of the condenser It and readszero when no torce is transmitted to the backing plate 1| by the coretube holder 25. However, when the insulating material Il is extruded sothat the core tube holder 2l is urged against the backing plate 1I, the.dielectric plates BI, 02 and Il are compressed so that the capacity otthe condenser Il is increased. This increase in capacity will bemeasured by the reading of the ammeter Il, which will indicate thepressure on the insulating material I I in extrusion passage 20 in theextruding head il. However, the dielectric plates ll, li, Il, Il and Mmay be compressed only slightly even under very high pressures so thatthe position of the core tube holder with respect to the forming die I3is not greatly aiTected.'

'Ihe condenser I9 is very durable and serves as an accurate means ofmeasuring the pressure of the insulating material i3 in the extrusionpassage 20 in the extruding head Il without adverse eiiect on theoperation of the extrusion appara- The pressure measuring apparatusdescribed hereinabove provides information for adjusting the extrusionapparatus. It may be used to test the extrudability of samples of aparticular batch oi' insulating material so that extrusion apparatus forextruding that batch may be adjusted accordingly. Also, it may be usedto provide accurate data concerning the extrusion characteristics ofcompounds whose ingredients vary in kind or proportion. The core tubeholder f5 may be made solid and the continuous extrusion apparatus maybe used to extrude samples of a batch of the insulating material lnorder to determinethe extrudability ot the batch so that a standardextrusion apparatus may be adjusted correctly without experimentationthereon. Also, articles of other types than insulating coverings, forexample, tubes, rods or strips, with or without inserts, may be extrudedby substituting suitable forming elements for the die 2l and the coretube n, and theumt p i of the ninas mural may be accuratelyreutigined bythe pressure measuring apparatus described hereinabove.

The pressure measuring apparat described hereinabove may be used tomeasure the unit extruding pressures of many types of plastic materials,for example, vulcanizable compounds including compounds of rubber orsynthetic rubberlike materials, such as Buna compounds, polymerizedchloroprene compounds, or the like. It likewise may be used withthermoplastic compounds made of polyethylene, polymerized vinylcompounds, such as vinyl halides. copolymers of vinyl halides and vinylacetate, polymerized vinylidine halides, cellulose acetate, celluloseacetates buty'rate or the like.

What is claimed is:

l. A condenser for measuring the pressure o! a material in a closedreceptacle having an aperture extending through the wall thereof, whichcomprises a hollow member designed to lit tightly into the apertureprovided in a wall of such a receptacle, a rod positioned slidablywithin the hollow member so that a portion thereof extends beyond eachend ot the member, a dielectric sleeve positioned over the end of therod ldiaeent to the interior portion ot the receptacle, a thrust washerpositioned slidably on the sleeve so that it abuts the adjacent end ofthe member. a pair of metallic plates positioned facewise on the sleeveand being movable with respect to the sleeve, a second thrust washerpositioned slidably on the sleeve adjacent to the innermost metallicplate, a plurality of dielectric plates interleaved with the metallicplates and the thrust washers. a cap secured on the end oi' the rod sothat it engages the second-mentioned thrust washer, and means secured onthe opposite end o! the md for causing the cap to press the metallicplates and the dielectric plates together, whereby am pressure directedoutwardly against the cap compresses the dielectric plates positionedbetween the metallic plates and thereby increas the capacity of thecondenser in proportion to the pressure exerted on the cap.

2. A condenser for measuring the pressure of a material in a closedreceptacle having an aperture extending through the wall thereof. whichcomprises a tubular member designed to ht tightly into the apertureprovided in a wall of such a receptacle, a rod positioned slidablywithin the tubular member so that a portion thereof extends beyond eachend of the member. a dielectric sleeve positioned on the end of the rodadiacent to the interior of the receptacle, a

.thrust washer positioned slidably on the sleeve so that it abuts theend of the member, a plurality of annular metallic plates positionedfacewise on the sleeve and designed to be movable with respect to thesleeve, a second thrust washer positioned slidably on the sleeveadjacent to the innermost metallic plate, a plurality oi' dielectricplates interleaved with the metallic plates and the thrust washers, acap secured on the end of the rod so that it engages thesecond-mentioned thrust washer, and means secured on the opposite end ofthe rod for causing the cap to press the metallic plates and thedielectric plates together, whereby any pressure directed o against thecap compr the dielectric platm positioned between the metallic platesand thereby increases the capacity of the condenser.

3. A condenser for measuring the pressure o!materialsinaclosedreceptaelehavinga accuse 'l threaded apertureextending through the wall thereof, which comprises a tubular memberthreaded at one end so that it may be ntted into the threaded apertureprovided in the wall of such a receptacle, a rod positioned slidablywithin the tubular member so that a portion thereof extends beyond theend of the member adjacent to the inner surface of the wall of thereceptacle, a dielectric sleeve positioned over the portion of the rodextending beyond the member and being of such length that one endthereof abuts the end of the member, a thrust washer positioned slidablyon the sleeve so that it abuts the end of the member,` a plurality ofmetallic plates positioned facewisc on the sleeve and designed to bemovable with respect to the sleeve, a second thrust washer positionedslidably on the sleeve adjacent to the innermost metallic plate, aplurality of dielectric plates interleaved with the metallic plates andthe thrust washers, a cap secured on the end of the rod adjacent to thesecond-mentioned thrust washer, means secured on the opposite end of therod for urging the rod outwardly with respect to the member and causingthe cap to hold the metallic plates and the dielectric plates on the endof the rod and DAVID D. JONES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 525,769 McElroy Sept. 11, 16941,646,236 Dubilier Oct. i6, 1927 1,717,051 Marshall June ll, 10291,801,203 Lecce Aprjl, 193i 2,436,946 Tatro -s Mar. 2, 1046

